This application is based on and claims priority to Japanese Patent Application No. 2000-111552, filed Apr. 13, 2000, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
The present invention is directed to internal combustion engines such as those used in outboard motors, and the engine control systems therefor.
2. Description of Related Art
An outboard motor generally includes a powerhead that consists of a powering internal combustion engine and a surrounding protective cowling. A drive shaft housing and a lower unit depends from the powerhead. The drive shaft housing and lower unit journals a drive shaft that is driven by the engine. A transmission, which drives a propulsion device in the lower unit, thereby propels an associated watercraft.
There are two general categories of fuel supply systems for internal combustion engines. One type of fuel system utilizes a carburetor, which delivers a generally constant air/fuel ratio during a given intake cycle. The other type of fuel system utilizes fuel injection, which delivers a finite amount of fuel to the engine generally once per combustion cycle. Typically, in a fuel injected engine, the fuel is either injected into the induction system or injected directly into the combustion chamber. The later method is generally referred to as direct fuel injection.
The current trend in the industry is to use direct fuel injection to improve the performance, emissions, and fuel economy of an outboard motor. One of the advantages of direct fuel injection is that the fuel/air ratio can be precisely controlled over a wide range of engine speeds and operating conditions. For example, direct fuel injection can be used to create a stratified charge in the combustion chamber (i.e., stratified direct fuel injection). To create a stratified charge, the fuel typically is directed towards the spark plug and fuel is injected just prior to ignition such that the fuel/air mixture is rich around the spark plug gap when the spark plug is fired. The engine can therefore be run at an overall leaner fuel/air ratio. This reduces the amount of unburned hydrocarbons in the exhaust and increases fuel economy, especially at low to medium engines speeds.
Direct fuel injection can also be used to create a pre-mixed charge in the combustion chamber (i.e., pre-mixed direct fuel injection). To create a pre-mixed charge in a two cycle engine, the fuel typically is injected into the combustion chamber before the closure of the exhaust port. This is allows sufficient time for the fuel to be diffused before ignition. In a similar manner, to create a pre-mixed charge in a four cycle engine, the fuel is typically injected into the combustion chamber before the intake valve is closed. Premixing tends to increase the output power of the engine particularly at high engine speeds.
Typically, in outboard motors, the exhaust gas emitted from the engine is discharged to the atmosphere through a propeller boss and into the body of water in which the watercraft is operating. This arrangement tends to aid in silencing the exhaust gases. However, the use of underwater discharge produces certain problems. For example, the back pressure (i.e., the pressure inside the exhaust passages) tends to fluctuate as the water level at the propeller boss fluctuates. Such back pressure fluctuations can cause the charging efficiency and air/fuel ratio to fluctuate thereby leading to poor fuel consumption and increased exhaust emissions.
Additionally, many outboard motors utilize engines with cylinders that are disposed horizontally. In such an engine, lubricant can accumulate within the engine and can be transmitted to the cylinders when the engine is started. This also can increase exhaust emissions.
As such, in the interest of obtaining even better emission control in outboard motors, catalysts have been added to the exhaust systems outboard motors. However, the performance of the catalyst is highly dependent upon the temperature of the exhaust gases. For example, the catalyst is typically not activated until the exhaust gas entering the catalyst reaches 170-300xc2x0 C. To achieve this temperature in the exhaust gas, the engine typically needs to be operating at engine speeds greater than 2000-3500 RPM. However, outboard motors are often operated for long periods of times at very low engines speeds or idle. During such periods, the exhaust temperature is usually about 100xc2x0 C. Such exhaust temperatures are inadequate for activating the catalyst. Moreover, such low exhaust temperatures and can deactivate a catalyst that has been previously activated.
One aspect of the present invention involves the realization that the temperature of the exhaust gas entering the catalyst can be increased by adjusting the fuel injection and/or ignition timing in the engine of the outboard motor. This is particularly useful when the outboard motor is operating at low load and/or low engine speeds.
In accordance with one aspect of the present the invention, a two-stroke internal combustion engine comprises a cylinder block defining a cylinder bore. A cylinder head is fixed at one end of the cylinder block enclosing one end of the cylinder bore. A crankcase member is fixed at the other end of the cylinder block and encloses the other end of the cylinder bore. The crankcase member defines a crankcase chamber. A piston is positioned in the cylinder bore. A crankshaft is rotably journaled in the crankcase and driven by the piston. The piston, the cylinder bore and the cylinder head together define a combustion chamber. At least one scavenge passage is formed in the cylinder block for transferring an air charge compressed in the crankcase to the combustion chamber. The scavenge passage comprises a scavenge port configured such that reciprocating motion of the piston opens and closes the scavenge port. An exhaust passage formed in the cylinder block is for discharging exhaust gases from the combustion chamber. The exhaust passage comprises an exhaust port configured such that the reciprocating motion of the piston opens and closes the exhaust port. A spark plug has one end exposed to the combustion chamber and is operatively connected to a control system. A fuel injector is disposed to inject fuel directly into the combustion chamber. The fuel injector includes an actuator that is operatively connected to the control system. An exhaust system is connected to the exhaust passage. The exhaust system includes a catalytic treatment device. The control system is configured, at least during low engine speeds, to finish injecting an amount of fuel into the combustion chamber before the exhaust port closes. The control system is also configured to increase a temperature of the exhaust gases when the temperature of the exhaust gases become insufficient to activate the catalytic treatment device.
In accordance with another aspect of the invention, a four-stroke internal combustion engine comprises a cylinder block that defines a cylinder bore. A cylinder head is fixed at one end of the cylinder block enclosing one end of the cylinder bore. A crankcase member is fixed at the other end of the cylinder block and encloses the other end of the cylinder bore. The crankcase member defining a crankcase chamber. A piston is positioned in the cylinder bore. A crankshaft is rotably journaled in the crankcase and is driven by the piston. The piston, the cylinder bore and the cylinder head together defining a combustion chamber. The engine including at least one intake port and intake passage for transferring an air charge to the combustion chamber and at least one exhaust port and exhaust passage for discharging exhaust gases from the combustion chamber. A spark plug has one end exposed to the combustion chamber and is operatively connected to a control system. A fuel injector is disposed to inject fuel directly into the combustion chamber. The fuel injector includes an actuator that is operatively connected to the control system. An exhaust system is connected to the exhaust passage. The exhaust system includes a catalytic treatment device. The control system is configured, at least during low engine speeds, to begin injecting fuel into the combustion chamber before the intake port closes. The control system also being configured to increase a temperature of the exhaust gases if the temperature of the exhaust gases is insufficient to activate the catalytic treatment device.
In accordance with yet another aspect of the present invention, a method for increasing an operating temperature of a catalytic treatment device in a two-stroke internal combustion engine, comprises injecting an amount of fuel into a combustion chamber of the engine before an exhaust port closes, at least during low engine speeds, and increasing the operating temperature by at least one of adjusting fuel injection through a fuel injector arranged to inject fuel directly into a combustion chamber and adjusting ignition timing.
In accordance with yet another aspect of the present invention, a method for increasing an operating temperature of a catalytic treatment device in a four-stroke internal combustion engine, comprises injecting an amount of fuel into a combustion chamber of the engine before an intake port closes, at least during low engine speeds, and increasing the operating temperature by at least one of adjusting fuel injection through a fuel injector arranged to inject fuel directly into a combustion chamber and adjusting ignition timing.
In accordance with still yet another aspect of the present invention, a two-stroke internal combustion engine comprises a cylinder block defining a cylinder bore. A cylinder head is fixed at one end of the cylinder block enclosing one end of the cylinder bore. A crankcase member is fixed at the other end of the cylinder block and encloses the other end of the cylinder bore. The crankcase member defines a crankcase chamber. A piston is positioned in the cylinder bore. A crankshaft is rotably journaled in the crankcase and driven by the piston. The piston, the cylinder bore and the cylinder head together define a combustion chamber. At least one scavenge passage is formed in the cylinder block for transferring an air charge compressed in the crankcase to the combustion chamber. The scavenge passage comprises a scavenge port configured such that reciprocating motion of the piston opens and closes the scavenge port. An exhaust passage formed in the cylinder block is for discharging exhaust gases from the combustion chamber. The exhaust passage comprises an exhaust port configured such that the reciprocating motion of the piston opens and closes the exhaust port. A spark plug has one end exposed to the combustion chamber and is operatively connected to a control system. A fuel injector is disposed to inject fuel directly into the combustion chamber. The fuel injector includes an actuator that is operatively connected to the control system. An exhaust system is connected to the exhaust passage. The exhaust system includes a catalytic treatment device. The engine further including means for increasing an operating temperature of the catalytic treatment device.
In accordance with another aspect of the engine, a four-stroke internal combustion engine comprises a cylinder block that defines a cylinder bore. A cylinder head is fixed at one end of the cylinder block enclosing one end of the cylinder bore. A crankcase member is fixed at the other end of the cylinder block and encloses the other end of the cylinder bore. The crankcase member defining a crankcase chamber. A piston is positioned in the cylinder bore. A crankshaft is rotably journaled in the crankcase and is driven by the piston. The piston, the cylinder bore and the cylinder head together defining a combustion chamber. The engine including at least one intake port and intake passage for transferring an air charge to the combustion chamber and at least one exhaust port and exhaust passage for discharging exhaust gases from the combustion chamber. A spark plug has one end exposed to the combustion chamber and is operatively connected to a control system. A fuel injector is disposed to inject fuel directly into the combustion chamber. The fuel injector includes an actuator that is operatively connected to the control system. An exhaust system is connected to the exhaust passage. The exhaust system includes a catalytic treatment device. The engine further including means for increasing an operating temperature of the catalytic treatment device.
In accordance with another aspect of the present invention, an internal combustion engine comprises a cylinder block defining a cylinder bore. A cylinder head is fixed at one end of the cylinder block and encloses one end of the cylinder bore. A crankcase member is fixed at the other end of the cylinder block and encloses the other end of the cylinder bore. The crankcase member defines a crankcase chamber. A piston is positioned in the cylinder bore. A crankshaft is rotably journaled in the crankcase and is driven by the piston. The piston, the cylinder bore and the cylinder head together define a combustion chamber. The engine also includes at least one intake port and intake passage for transferring an air charge to the combustion chamber and at least one exhaust port and exhaust passage for discharging exhaust gases from the combustion chamber. A spark plug has one end exposed to the combustion chamber and is operatively connected to a control system. A fuel injector is disposed to inject fuel directly into the combustion chamber. The fuel injector includes an actuator that is operatively connected to the control system. An exhaust system is connected to the exhaust passage. The exhaust system includes a catalytic treatment device, the control system is configured to form a substantially premixed air/fuel charge at ignition during low engine speeds and to form a substantially stratified fuel-air charge at ignition during higher engine speeds.
In a accordance with another aspect of the present invention, a method for increasing an operating temperature of a catalytic treatment device in an internal combustion engine comprises forming a substantially pre-mixed air/fuel charge at ignition during low engine speeds and forming a substantially stratified fuel-air charge at ignition during higher engine speeds.
These and other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiments disclosed.